Automatic buoyancy compensation system



April 23, 1968 K. kEAYs ET AL 3,379,156

AUTOMATIC BUOYANCY COMPENSATION SYSTEM I Filed Dec. 5, 1966 2 Sheets-Sheet 1 INVENTORS KEATINGE KEAYS RAYMOND L. COLECHIA April 23, 1968 K. KEAYS ET AL 3,379,155

AUTOMATIC BUOYANCY COMPENSATION SYSTEM Filed Dec. 5, 1966 2 Sheets-Sheet 2 TO SUBMARINE AIR SYSTEM TO AND FROM SEA WEIGHT [/bS. X [000/ o I I o s 10 1s 20 PT 05 H (feet X I000) INVENTORS KEATINGE KEAYS F BY RAYMOND L. COLECHIA ATTORNEY United States Patent 3,379,156 AUTOMATIC BUOYANCY COMPENSATION SYSTEM Keatinge Keays, Groton, and Raymond L. Colechia, Mystic, Conn., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Dec. 5, 1966, Ser. No. 599,685 7 Claims. (Cl. 114-16) ABSTRACT OF THE DISCLOSURE Greater design strengths required in deep-diving submarines render them less compressible in the Water manifesting a steadily increasing buoyancy as the submarine descends. To compensate for this increase, compressed air tanks are added to the outside of the pressure hull and filled to predetermined pressures. A floating-ball check valve in each tank admits ambient sea water as the vehicle descends. As the vehicle ascends, the Water is expelled from the tanks but the compressed air remains entrapped. In this manner, the vehicle ballast varies approximately in direct proportion to the buoyancy over the entire depth range.

The present invention relates to submarines and more particularly to an automatic buoyancy compensation and compressed gas storage system for deep-diving submarines.

Contrasted to conventional submarines which are designed to operate at relatively shallow depths, the deepdiving submarine must withstand great ambient pressures. This requires a so-called hard pressure hull design in which the compressibility of the hull is less than of sea water. The result is a pressure hull which has a buoyancy that increases with depth; that is, the submarine becomes positively buoyant as it descends. From neutral buoyancy at the surface, this change can be substantial. For example, in the deep-diving submarine Aluminaut the total change in buoyancy is about 3,000 pounds in descending from the surface to a depth of 10,000 feet.

Conventional shallow-diving submarines usually take aboard or discharge water for ballast compensation. However, at greater depths such as below 10,000 feet, pumping the Water ballast overboard is virtually prohibitive because it requires heavy machinery and consumes much power. Alternatively, as is done in the Aluminum, the submarine is loaded with an amount of shot ballast sufiicient to compensate for the change in buoyancy to be experienced in a given dive, and the submarine does down heavy until it reaches neutral buoyancy. To ascend, the shot ballast must be dropped into the sea such as by electromagnetically controlled release valves. This latter technique requires that the maximum depth of a given dive be determined before the dive is started, and the submarine must proceed to this deepest depth first. If a dive is planned and the submarine shot-ballasted for 10,000 feet, it is not possible to achieve 13,000 feet or 15,000 feet on that dive no matter how desirable it might be. Furthermore, everytime the submarine makes a deep dive a large amount of shot ballast must be expended involving both an expense in the value of the ballast and in the effort required to re-ballast for the next dive. If it is desired to increase depth radically, such as more than 1,000 feet, the submarine must surface and add shot ballast.

It is a general purpose of the present invention to provide a novel and improved buoyancy compensating system for deep-diving submarines which will enable the submarine to increase depth radically while maintaining substantially neutral buoyancy. Briefly, this is accomplished 3,379,156- Patented Apr. 23, 1968 with a plurality of compressed air tanks secured on the outside of the pressure hull of the submarine, each tank being of a predetermined volume and filled initially with air to a predetermined pressure. A floating-ball check valve positioned at the bottom of each tank sequentially admits ambient sea water into the respective tanks as the submarine descends and as the water pressure exceeds the particular air pressure in each tank. As the submarine ascends the sea water is expelled from the tanks in reverse order. The check valve prevents escape of the pressurized air.

Accordingly, it is an object of the present invention to provide a deep-diving submarine buoyancy compensating system which will operate at relatively great depths with out requiring heavy machinery or high power consumption.

Another object of the invention is to provide a novel and improved buoyancy compensating system for extending the range of depth per dive over which deep-diving submarines operate.

Still another object of the invention is to provide a new and improved buoyancy compensating system for submarines which is relatively inexpensive, easy to adapt to existing submarines and ballast systems, and which is relatively low in cost to maintain and operate.

Various other objects and advantages will appear from the following description of one embodiment of the invention, and the most novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the drawing:

FIG. 1 represents a longitudinal view in elevation of a deep-diving submarine with a fragment broken away to illustrate compressed air tanks as applied in accordance with the invention;

FIG. 2 represents an isometric view of one of the air tanks of FIG. 1 with a fragment cut away to illustrate a floating-ball check valve as applied in accordance with the invention;

FIG. 3 schematically represents the manner according to the invention in which the air tanks of FIG. 1 are connected; and

FIG. 4 graphically illustrates a typical relationship of buoyancy and compensating ballast according to the invention.

Referring now to FIG. 1 of the drawing, a deep-diving submarine 10 is shown as having a so-called hard pressure hull 11 wherein its buoyancy becomes more positive as it descends in sea water. An unpressurized compartment 12 secured beneath the pressure hull 11 contains inter alia three spherical tanks 13, 14 and 15 which are initially filled with a compressed gas such as air. The actual number of tanks, and volume and gas pressure within each tank are determined in a manner described hereinbelow.

As further illustrated schematically in FIG. 3, the inside of each tank 13, 14, 15 communicates at the bottom through a floating-ball check valve 18, 19, 20 to a common header conduit 17 which in turn connects directly with the ambient sea water immediately beneath the compartment 12.

Only the details of check valve 18 of the tank 13 as illustrated in FIG. 2 will be described, check valves 19 and 20 of tanks 14 and 15, respectively, being identical thereto. The valve comprises a ball 22 which floats in sea Water and a seat ring 23 for receiving the ball when the valve is closed. A ball cage 24 fixed about the ring 23 confines the ball 22 over the ring 23 to ensure seating. The particular materials selected and design details of the valves 18, 19, 20 are not critical to the invention except to the extent they are recited in the appended claims. Aluminum and titanium balls have been found satisfactory inasmuch as they can be made to weigh less than sea water and hence will float, and simultaneously provide suflicient strength to resist submergence pressures to 30,000 feet. Various phenolic and cast polyester materials are satisfactory for the ring 23 as they provide sufficient compressive strength to form a positive gas seal when the sea water has been expelled from the tank and gravity has forced the ball to seat.

As illustrated in FIG. 3, when filled with air the compressed gas tanks 13, 14 and 15 also serve as compressed air storage tanks for other purposes such as blowing water ballast tanks, not shown. These ballast tanks are used to increase the submarines weight to neutral buoyancy at the surface before diving. Conduits 26, 27 and 28 and their associated valves 29, 3t) and 31, therefore, provide appropriate connections for such other purposes. Valves 32, 33 and 34 close off communication of tanks 13, 14, 15 to prevent sea water flow when the air is bled through conduits 26, 27, 28.

Each spherical tank 13, 14, 15 is designed for a discrete volume and initially filled with compressed gas at a predetermined pressure. The number of tanks, their volumes, and the initial gas pressure in each is selected so that the submarines lost displacement, i.e. total amount of water taken into the tanks, at any given depth will closely approximate the incremental increase in buoyancy at that depth. One technique for matching lost displacement to increased buoyancy will be described with reference to FIG. 4 of the drawing. The solid-line curve postulates the actual compressibility characteristic of one deep-diving submarine in terms of increase buoyancy versus depth. Of course the slope of the curve is merely representative and will vary with different hull configurations and designs. The broken-line curve of FIG. 4 represents total lost displacement versus depth of the tanks 13, 14 and 15. The volume and initial pressure of each tank was selected by trial and error to fit or closely match the lost displacement curve to the increased buoyancy curve of FIG. 4. So that the submarinewould not become more than 100 pounds light or heavy throughout its diving range, the selection resulted in the following values:

Tank N0. Volume cu. ft. Initial Gas Valve Opening Pressure, p.s.i.g. Depth, feet A mathematical approximation of the total lost displacement curve can be obtained using Boyles Law for perfect gases at constant temperature (p V =p V for t-=C).'The total lost displacement, TLD, for tanks 13, 14 and 15 is expressed as follows:

Where,

w =density of water V V and B =volumes of tanks 13, 14 and 15,

p p and p =initial gas pressure in tanks 13, 14 and 15, and

p =instantaneous depth of the submarine.

Each bracketed term of the equation, such as 13 (PD-P13) diving, the water ballast tanks are flooded with surrounding sea water and the submarine, now in slightly negative buoyancy, begins to submerge at a relatively constant rate. As it descends, the buoyancy begins to go positive again and approach neutral. At a depth of about 34 feet the sea water pressure equals the gas pressure in tank 13, and check valve 13 opens to admit water into the tank and cause the ball 22 to rise off its seat. As the water reduces the air volume in tank 13, the gas pressure increases and additional submergence is required to increase the water pressure and allow additional water to enter the tank. The weight of the Water admitted at any given depth between 34 feet and 5306 feet at which depth the check valve 19 opens in tank 14 approximately offsets the increase in buoyancy of the submarine thereby maintaining neutral buoyancy.

At about 5306 feet of depth, the water pressure equals the gas pressure in the tank 14 and check valve 19 opens to admit Water and progressively displace air volume as the submarine continues to submerge. Similarly, check valve 20 in tank 15 opens at about 10,400 feet.

Since the total lost displacement maintains approximately neutral buoyancy, it is contemplated that ascent or descent would be effected by conventional submarine propulsion motors.

To resurface from neutral buoyancy at an operating depth, the propulsion system must provide just enough upward force to cause the submarine to rise. As it rises, the ambient water pressure decreases relative to the pressure in tanks 13, 14 and 15 causing water to be expelled back to the sea. The check valves 18,19 and 20 close when the water in each tank has been completely discharged and the initial gas pressure exceeds the ambient water pressure. This occurs in the reverse order in which the valves opened during the submarines descent. When the submarine has resurfaced, the gas in each tank 13, 14, 15 may then be used to blowthe water ballast tanks to restore substantial positive buoyancy of the submarine. A normally open valve 32 is provided for closing off the sea water to the header 17 when the compressed gas in the tanks 13, 14 and 15 is used to blow the water ballast tanks.

An emergency ballast system such as a releasable lead weight is also contemplated, but not shown, which can be dropped from the submarine from'beneath the surface if the conventional propulsion system should become inoperative.

Some of the many advantages of the above-described invention should now be apparent. For example, the use of expensive and 1abor-consuming shot ballast systems for obtaining desired operating depths has been obviated by a water ballast system which automatically compensates for changes in buoyancy from neutral throughout all of the designed operating depths. The. commander of a submarine may now submerge from higher to lower depths without resurfacing for additional, shot ballast. There is no requirement for heavy machinery and high power consumption in order to discharge water ballast at great depths in order to ascend. The invention is also ideally suited for adaptation to existing submarine compressed air storage systems. The system consumes very little power and is especially adaptable for use in deep submergence programs.

It will be understood that various changes in the details, materials, steps and arrangement of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. An automatic buoyancy compensation system for a deep-diving submarine of the type having a compressibility less than ambient sea water, comprising:

tank means formed to be secured to the outside of the subniarines hull for storing a compressed gas, said tank means having an opening formed therein 5 at the bottom directly communicating with the ambient sea water; and

first valve means secured to said tank means in said opening responsive to the pressure differential at said opening between the sea water and the gas for controlling flow therethrough, and including a valve seat secured to the inside of said tank means around said opening, and a floatable element inside said means and normally urged into said valve seat for closing said opening when said tank means is completely filled with gas to a pressure exceeding that of the ambient sea water;

whereby the total Weight of the sea water contained in said storage means at any given depth is substantially equal to the increase in buoyancy of the submarine at such depth.

2. A system according to claim 1 wherein said first valve means further comprises:

cage means secured to the inside of said tank means about said opening for confining movement of said element to the vicinity of said valve seat when there is sea water in said tank means.

3. A system according to claim 2 wherein said tank means is constructed of a predetermined volume and initially filled with said gas to a predetermined pressure for providing lost displacement substantially equal to the increase in buoyancy as the submarine descends.

4. A system according to claim 3 further comprising:

second valve means operatively connected in series with said first valve to the outside of said tank means for selectively shutting 01f flow therethrough; and

third valve means operatively connected to the top of said tank means for controlling gas flow therefrom and adapted to be connected to the submarines gas system.

5. An automatic buoyancy system for a deep-diving submarine of the type having a compressibility less than sea water, comprising:

a plurality of tanks formed to be secured to the outside of the submarines hull for storing compressed gas; and

a valve at the bottom of each of said tanks for controlling sea water flow into and out of each of said tanks, and including a valve element of a density less than the sea water in its associated tank urged into a normally closed position when said associated tank is completely filled with gas to a pressure exceeding that of the ambient sea Water and into a normally open position when partially filled with sea Water;

whereby the total Weight of sea water contained in said plurality of tanks at any given depth is substantially equal to the increase in buoyancy of the submarine at such depth.

6. A system according to claim 5 wherein each of said tanks is constructed with a discrete predetermined volume and initially filled With gas to a discrete predetermined pressure for providing a total lost displacement in said tanks substantially equal to the increase in buoyancy of the submarine throughout its diving range.

7. A system according to claim 5 further comprising:

a first plurality of shut-01f valves each connected in series with each of said check valves for selectively shutting off flow therethrough; and

a second plurality of shut-off valves each operatively connected to the top of a respective one of said tanks for controlling gas flow therethrough and adapted to be connected to the submarines gas system.

References Cited UNITED STATES PATENTS 2,117,003 5/ 1938 Hasselmann 1 14-16 3,171,376 3/1965 Sellner et al. 11416 3,195,493 7/1965 Lacam et al 11416 MILTON BUCHLER, Primary Examiner. TRYGVE M. BLIX, Examiner. 

